Resistive memory, such as resistive random access memory (ReRAM or RRAM) generally includes a plurality of resistive memory cells. Such cells may be in the form of a two terminal device in which a comparatively insulating switching layer or medium is positioned between two conductive electrodes. In some instances, such devices include one transistor (1T) or one diode (1D) along with one resistor (1R), resulting in 1T1R or 1D1R configurations. The resistive memory cells of RRAM can change between two different states in response to a voltage, namely a high resistance state (HRS) which may be representative of an OFF or 0 state; and a low resistance state (LRS) which may be representative of an ON or a 1 state.
Some resistive memory devices operate based on the formation and breakage of filamentary channels (hereinafter, filaments) within the switching layer of individual resistive memory cells. Such devices, referred to herein as filamentary resistive memory, require the execution of an initial forming process, during which a relatively high voltage stress (known as a forming voltage) is applied to a memory cell precursor. During the application of the forming voltage, at least some vacancies within the switching layer redistribute to form one or more filaments that provide a low resistance pathway between the conductive electrodes of the cell. The resulting resistive memory cell may then be toggled between a high and low resistive state by the application of a reset and set voltage, respectively.
As may therefore be appreciated, some filamentary resistive memory cells are manufactured by applying a forming voltage to a switching layer precursor that includes oxygen vacancies that are distributed therein. Although such processes have shown promise, they generally rely on the use of cell precursors that offer limited control over the distribution of oxygen vacancies in the switching layer precursor. As a result, such processes also offer limited control over the geometry or other characteristics of the filament(s) formed by application of the forming and/or SET voltage. Moreover in some instances, such processes rely on precursors that include an oxygen exchange layer to react with oxygen in the switching layer precursor to produce oxygen vacancies, e.g., in an annealing process. Although effective to produce oxygen vacancies, in many instances some portion of the OEL may remain unreacted after the annealing process. When present the residual unreacted OEL may further react with oxygen in the switching layer produced by the forming process, potentially changing the performance characteristics of the resistive memory cell over time. This can be of particular concern in instances where the OEL is manufactured from the same material as an overlying electrode.
Although the following Detailed Description will proceed with reference being made to illustrative embodiments, many alternatives, modifications, and variations thereof will be apparent to those skilled in the art.